The forebrain exerts executive control over the midbrain pathway that mediates auditory orienting behavior. The functions of this control are not known but are likely to include the effects of attention and target selection. The processing of information in the forebrain and midbrain pathways that contributes to orienting behavior has been well studied, and these pathways have been shown to be anatomically interconnected. Yet, the functional interactions between these pathways are not well understood. The focus of this application is to study the influences of the forebrain pathway on the midbrain pathway for gaze control in the barn owl. The output of the forebrain pathway will be manipulated with electrical microstimulation. The effects of these manipulations on midbrain unit responses to auditory stimulation will be evaluated for changes in tuning, response gain, and sensitivity. In addition, the site in the auditory pathway at which gain modulation occurs and the neurotransmitters responsible for such changes will be identified. Exploring the interaction between these well-characterized pathways may uncover fundamental strategies and mechanisms for modulating sensory processes. Such mechanisms may contribute to attention generally in the brain. Understanding mechanisms of sensory modulation may provide insight to optimal therapeutic approaches for remediating the effects of certain kinds of mental illness. [unreadable] [unreadable]